CVE-2026-64620

A heap-based buffer overflow in FreeRDP's crypto_rsa_common() allows an unauthenticated remote attacker to trigger a denial of service or potential remote code execution. By sending a crafted ciphertext during RDP Standard Security key establishment, the attacker can force a data write before the size is validated, resulting in memory corruption.

An unauthenticated remote attacker can trigger a heap buffer overflow in FreeRDP by sending a crafted ciphertext during key establishment.

Red Hat rates this vulnerability as Important rather than Critical due to inherent mitigations in Red Hat environments. Specifically, RHEL's built-in memory defenses (such as glibc heap hardening) reliably reduce the threat of remote code execution down to a localized service crash (Denial of Service). Furthermore, the flaw is only reachable if an administrator explicitly configures the server to use the non-default, legacy "RDP Standard Security.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate, explicitly disable legacy RDP Standard Security and enforce Network Level Authentication (NLA/TLS) on the server. Additionally, restrict network access to trusted clients via firewalls, or disable the FreeRDP service entirely if not needed, remembering to restart the service to apply any configuration changes.